Key knife



FIG. 1 is a perspective front view of the key knife, showing my new design;

FIG. 2 is a front view thereof; the back view being a mirror image thereof;

FIG. 3 is a right side view thereof; the left side view being a mirror image thereof;

FIG. 4 is a top view thereof; and,

FIG. 5 is a bottom view thereof. 

CLAIM The ornamental design for a key knife, as shown and described. 